Thirty-one major cities, including the likes of London, Barcelona and Milan, have signed a declaration committing to investment in green spaces and fighting the effects of climate change.

Mayors of each city signed up to the C40 cities network goal of having 30-40 per cent of built-up city surface consisting of green spaces like parks or streets lined with trees, or permeable spaces to absorb water and prevent flooding.

Other commitments include improving access to these green spaces for locals.

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